Cut the nori into squares with scissors and add to the pan. Trim and thinly slice the green onions and add to the pan. Cube the tofu and add to the pan. Add the peas. Turn up the heat and bring the soup to a strong simmer.

Meanwhile, put the miso into a small bowl, add a little hot water from the kettle, and whisk until smooth. When the soup is simmering, take it off the heat and stir the miso into the soup. (This is so it doesn't clump.)